I want to know if is possible to connect dc motor directly to dc bus. I don't know if is possible to eliminate the converter and make use of DC Motor directly.
Yes, but in this case you will lose the capability to control motor speed, which is generally performed through the converter regulating the armature current.
If uncontrolled operation is OK for you then you can go with direct connection to the bus.
If you still want to achieve some level of controllability, allow me to suggest to have a look at my paper " Analysis of a fault-tolerant hybrid-excitation DC motor " here on RG: we proposed to have the armature directly connected to the DC bus, while auxiliary excitation windings (wound around the PMs of the DC motor) are supplied by dedicated converter (of small power) and provide the possibility to control the field and thus the speed of the motor.
Article Analysis of a fault-tolerant hybrid-excitation DC motor